Number of 3X3 1..n+1 arrays with positive determinant.

Terms

a(0) =132a(1) =7854a(2) =116520a(3) =916860a(4) =4820439a(5) =19624035a(6) =65713455a(7) =190759077a(8) =493962822a(9) =1168477251a(10) =2559841278a(11) =5270707320a(12) =10278584778a(13) =19140242421a(14) =34233601737a(15) =59117179833a(16) =98911520802a(17) =160982370882a(18) =255478326648a(19) =396430119123